Probe into emissions scandal:Bosch

German auto supplier Robert Bosch [ROBG.UL] said it had launched an internal probe to investigate whether any of its staff were involved in a scandal over the rigging of automotive emissions tests.

Stuttgart-based Bosch, which released preliminary full-year earnings on Wednesday, makes a diesel engine management program used by several top automakers including Volkswagen <VOWG_p.DE>, which is under investigation by German prosecutors and U.S. authorities.

Bosch is looking into its role in Volkswagen's efforts to circumvent U.S. diesel emissions tests.

"The day after the allegation became public, I ordered an internal investigation," Chief Executive Volkmar Denner said, adding the company was cooperating with authorities and could not provide further details on the probe.

Bosch is also under investigation by Stuttgart prosecutors and U.S. authorities.

Denner said it would be wrong to dismiss diesel as a fuel-saving technology in the wake of the scandal. Combined with modern filter systems, diesel engines can even help reduce emissions in large cities by reducing particulate matter.

"The diesel is an air cleaning machine," Denner said.

Separately, Bosch said it continued to expect a rise in operating profit in 2016 as demand for driver assistance and infotainment systems helped lift the company's full-year sales and profit margin in 2015.

The industrial group, which makes household goods, engine components and sensor technologies, said its revenue rose 7 percent year-on-year to 70.6 billion euros ($76.7 billion) in 2015 thanks to a 12 percent jump in sales from its mobility solutions division to 41.7 billion euros.

Preliminary results for the first time included proceeds from two joint-venture companies, Bosch Siemens Haushaltsgeraete [BSHBS.UL] and ZF Lenksysteme, which Bosch acquired in 2014, boosting revenues by 16 billion euros, the company said.

The shift towards more fuel-efficient and safer cars has helped unlisted Bosch boost sales of gasoline and diesel injection systems and to sell more high-margin products. Revenue from the sale of automotive radar and assistance systems doubled, Bosch said.

Driver assistance systems, including ultrasound, radar and video sensors are used in crash-avoidance technology and will become important components for auto makers to launch self-driving cars.

Overall, the group's operating margin widened to 6.5 percent in 2015 from 5.8 percent in the year-earlier period, Bosch said.